\documentclass[UTF8]{ctexart}
\usepackage[a3paper,left=0cm,right=0cm,top=0cm,bottom=0cm,landscape]
{geometry}
\usepackage{graphicx}
\def\xmuspace{\hbox{}\vfill\hbox{}\par}
\begin{document}
\hspace{0.471\textwidth}
\noindent
    \begin{minipage}{0.85\ccwd}\zihao{-5} % 0.85 just fine
    \xmuspace
    论文名称
    \xmuspace
    作者姓名 
    \xmuspace
    指导教师 
    \xmuspace
    张三
    \xmuspace
    厦门大学
    \xmuspace
\end{minipage}
\begin{minipage}{0.5\textwidth}
    \IfFileExists{../example/demo.pdf}{
        \includegraphics[width=\textwidth]{../example/demo.pdf}
        }{
            \IfFileExists{../example/temp/demo.pdf}{
                \includegraphics[width=\textwidth]{../example/temp/demo.pdf}
            }{
                Plese choose the right picture place!!!
            }
        }
\end{minipage}%
\end{document}
